idlj: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/debug/usr/lib/jvm/java-7-openjdk-amd64/bin/idlj - from package: openjdk-7-dbg
/usr/lib/jvm/java-7-openjdk-amd64/bin/idlj - from package: openjdk-7-jdk

You may install the required package with command apt-get install {package}

Error in other languages:
idlj: bevel nie gevind nie
idlj: comandă negăsită
idlj: comando não encontrado
idlj: commande introuvable
idlj: command not found
idlj: käsku ei ole
idlj: không tìm thấy lệnh
idlj: komanda nerasta
idlj: Kommando nicht gefunden.
idlj: kommandot finns inte
idlj: komut yok
idlj: nie znaleziono polecenia
idlj: níor aimsíodh an t-ordú
idlj: no se encontró la orden
idlj: no s'ha trobat l'ordre
idlj: opdracht niet gevonden
idlj: parancs nem található
idlj: perintah tidak ditemukan
idlj: príkaz nenájdený
idlj: příkaz nenalezen
idlj: команда не найдена
idlj: командата не е открита
idlj: 命令找不到
idlj: コマンドが見つかりません